In recent years, in view of energy saving and environmental conservation, illumination apparatus (such as LED bulbs and LED fluorescent tubes) using a light-emitting diode (hereinafter also referred to as “LED”) as a light source have been increasingly replacing electric light bulbs and fluorescent tubes.
In commonly used LED fluorescent tubes, a plurality of LEDs are disposed on a substrate at a predetermined interval, and a cover is disposed so as to cover the LEDs (see, for example, PTL 1).
PTL 1 discloses an LED illuminating apparatus in which an LED disposed on a substrate is covered. The LED illuminating apparatus disclosed in PTL 1 includes a substrate, a plurality of LEDs disposed in a line on the substrate, a cylindrical lens having a ridgeline extending along the arrangement direction of the LEDs, and a light transmission cover disposed to cover a plurality of LEDs and the cylindrical lens.
With the LED illuminating apparatus disclosed in PTL 1, light emitted from the LEDs is spread by the cylindrical lens in a direction perpendicular to the arrangement direction of the LEDs. The light having passed through the cylindrical lens passes through the light transmission cover and then emitted to the outside.